1. Field of the Invention
The present invention relates to conveyor belts and, in particular, to a conveyor belt capable of traversing horizontal curves during its conveying run while still allowing for retention of the material to be conveyed thereon, the conveyor belt being made of a stretchable or elongatable elastomeric material and including upper and lower layers of reinforcing material.
2. Description of the Prior Art
As is known, conveyor belts have been developed for traveling through an orbit with a generally horizontally extending conveying run overlying a generally horizontally extending return run with the conveying and return runs being stretched or elongated to provide tension in the sides of the conveying run so that such sides remain in tension as the conveying run traverses a horizontal curve. A description of such a tensioned conveyor belt is set forth in U.S. Pat. No. 4,387,801 wherein one embodiment of a conveyor belt is disclosed and described having a selected limited elongation for establishing the overall length of an orbital conveyor belt. A conveyor belt including an internal stretch limiter and an upper and lower layer of reinforcing material is disclosed in Marshall U.S. Pat. No. 5,004,098.
A problem with the prior art conveyor belts is that the belt ants to roll out from under edge roller flanges which are intended to hold the belt in turns. Further, the belt wants to lift out from under the edge roller flanges and go straight up in severe dips. The force that the flanges exert on the belt prevent this, but in order for this to be effective, the belt must be relatively stiff. However, in order to take a troughed shape so as to effectively carry material, the belt has to be relatively flexible. The problem thus has been to make the belt flexible enough to trough, but relatively stiff to help resist buckling in the opposite direction. This has resulted in a compromise design. Present conveyor belts have two layers of reinforcing cords near the bottom surface, and two layers near the top surface, and all four of the cords that constitute these layers are the same size. The purpose of this reinforcement is to provide the required stiffness.